19 research outputs found
Toroidal horizons in binary black hole mergers
We find the first binary black hole event horizon with a toroidal topology. It has been predicted that generically the event horizons of merging black holes should briefly have a toroidal topology. However, such a phase has never been seen in numerical simulations. Instead, in all previous simulations, the topology of the event horizon transitions directly from two spheres during the inspiral to a single sphere as the black holes merge. We find a coordinate transformation to a foliation of spacelike hypersurfaces that “cut a hole” through the event horizon surface, resulting in a toroidal event horizon, thus reconciling the numerical work with theoretical expectations. The demonstration requires extremely high numerical precision, which is made possible by a new event horizon code described in a companion paper. A torus could potentially provide a mechanism for violating topological censorship. However, these toroidal event horizons satisfy topological censorship by construction, because we can always trivially apply the inverse coordinate transformation to remove the topological feature
Parallel adaptive event horizon finder for numerical relativity
With Advanced LIGO detecting the gravitational waves emitted from a pair of merging black holes in late 2015, we have a new perspective into the strong field regime of binary black hole systems. Event horizons are the defining features of such black hole spacetimes. We introduce a new code for locating event horizons in numerical simulations based on a Delaunay triangulation on a topological sphere. The code can automatically refine arbitrary regions of the event horizon surface to find and explore features such as the hole in a toroidal event horizon, as discussed in our companion paper. We also investigate various ways of integrating the geodesic equation and find evolution equations that can be integrated efficiently with high accuracy
What does a binary black hole merger look like?
We present a method of calculating the strong-field gravitational lensing
caused by many analytic and numerical spacetimes. We use this procedure to
calculate the distortion caused by isolated black holes and by numerically
evolved black hole binaries. We produce both demonstrative images illustrating
details of the spatial distortion and realistic images of collections of stars
taking both lensing amplification and redshift into account. On large scales
the lensing from inspiraling binaries resembles that of single black holes, but
on small scales the resulting images show complex and in some cases
self-similar structure across different angular scales.Comment: 10 pages, 12 figures. Supplementary images and movies can be found at
http://www.black-holes.org/the-science-numerical-relativity/numerical-relativity/gravitational-lensin
Toroidal horizons in binary black hole mergers
We find the first binary black hole event horizon with a toroidal topology. It has been predicted that generically the event horizons of merging black holes should briefly have a toroidal topology. However, such a phase has never been seen in numerical simulations. Instead, in all previous simulations, the topology of the event horizon transitions directly from two spheres during the inspiral to a single sphere as the black holes merge. We find a coordinate transformation to a foliation of spacelike hypersurfaces that “cut a hole” through the event horizon surface, resulting in a toroidal event horizon, thus reconciling the numerical work with theoretical expectations. The demonstration requires extremely high numerical precision, which is made possible by a new event horizon code described in a companion paper. A torus could potentially provide a mechanism for violating topological censorship. However, these toroidal event horizons satisfy topological censorship by construction, because we can always trivially apply the inverse coordinate transformation to remove the topological feature
Parallel adaptive event horizon finder for numerical relativity
With Advanced LIGO detecting the gravitational waves emitted from a pair of merging black holes in late 2015, we have a new perspective into the strong field regime of binary black hole systems. Event horizons are the defining features of such black hole spacetimes. We introduce a new code for locating event horizons in numerical simulations based on a Delaunay triangulation on a topological sphere. The code can automatically refine arbitrary regions of the event horizon surface to find and explore features such as the hole in a toroidal event horizon, as discussed in our companion paper. We also investigate various ways of integrating the geodesic equation and find evolution equations that can be integrated efficiently with high accuracy
SpECTRE: A Task-based Discontinuous Galerkin Code for Relativistic Astrophysics
We introduce a new relativistic astrophysics code, SpECTRE, that combines a
discontinuous Galerkin method with a task-based parallelism model. SpECTRE's
goal is to achieve more accurate solutions for challenging relativistic
astrophysics problems such as core-collapse supernovae and binary neutron star
mergers. The robustness of the discontinuous Galerkin method allows for the use
of high-resolution shock capturing methods in regions where (relativistic)
shocks are found, while exploiting high-order accuracy in smooth regions. A
task-based parallelism model allows efficient use of the largest supercomputers
for problems with a heterogeneous workload over disparate spatial and temporal
scales. We argue that the locality and algorithmic structure of discontinuous
Galerkin methods will exhibit good scalability within a task-based parallelism
framework. We demonstrate the code on a wide variety of challenging benchmark
problems in (non)-relativistic (magneto)-hydrodynamics. We demonstrate the
code's scalability including its strong scaling on the NCSA Blue Waters
supercomputer up to the machine's full capacity of 22,380 nodes using 671,400
threads.Comment: 41 pages, 13 figures, and 7 tables. Ancillary data contains
simulation input file
Ulcerative pododermatitis and disseminated erosive lesions associated with cowpox virus infection in a domestic cat
The authors report on a case of feline cowpox virus infection associated with severe ulcerative dermatitis of a paw and disseminated erosive lesions. While the anamnesis of the cat being a known rodent-hunter, a typical seasonality of infection and the progression of clinical signs from a primary anterior lesion (forelimb) indicated a possible cowpox virus infection, the differential diagnosis was complicated by the resemblance of clinical signs to those induced by feline herpesvirus-dermatitis or feline calicivirus infection. These differential diagnoses were excluded by means of immunostaining and PCR, respectively. Detection of eosinophilic intracytoplasmic inclusion bodies in cells from biopsy material and positive PCR and sequencing results confirmed the diagnosis of cowpox virus infection. Genetic characterisation of the isolate, based on the highly diverse haemagglutinin gene, showed that the strain (Liege 2015; GenBank accession number: KU726584) clustered with other European isolates, mostly from exotic zoo animals